By branding political extremists “socialists” or “conservatives” we allow them the entry into the mainstream that they crave.

Hitler wasn’t a socialist. I’ve never spoken to him about it, obviously, but I think I’m on safe ground here.

In the past week, a debate began chugging along merrily following the suspension of Rachel Frosh from the Tory party candidates’ list. Frosh’s crime was to retweet the kind invitation “Dear Socialists, embrace your inner Nazism”, followed by a link to Adolf channelling his inner Keir Hardie: “We are Socialists, we are enemies of today’s capitalistic economic system,” the wannabe dictator said in 1927. Cue lots of excited blogging about how Hitler has spent the past 80 years giving the right a bad name, when he was just a poor man’s Nye Bevan.

“There is an accepted mainstream view that the origins of Nazism lie in socialism, or that they have common roots,” Frosh wrote in a piece for one right-wing website. Her definition of the “accepted mainstream” turned out to be something about Hayek written on Wikipedia.

“I believe Nazisim [sic] and Fascism to have far more in common with socialism than conservatism,” wrote the blogger Iain Dale. “The clue is the phrase ‘National Socialism’.” On which basis, the German Democratic Republic was presumably a flourishing democracy.

According to the Conservative MEP Daniel Hannan, “Almost everyone in those days accepted that Fascism had emerged from the revolutionary left.” Which is true, so long as you ignore what happened to Hitler’s old comrades during the Night of the Long Knives.

Anyone who has studied Hitler’s rise to power knows he was no socialist. He was an opportunist, even a political schizophrenic. Which served him well, because in a Weimar Republic struggling – and failing catastrophically – to come to terms with military humiliation, a crisis of national identity and an economic implosion, ideology was a moveable feast. Indeed, it was so moveable, it opened the door to Hitler’s rise to power. “Who cares what he thinks?” Germany said to herself. “He’ll do for now.”

Pin the ideology on the Führer is a fun game. Actually, it’s quite a tasteless game. But we can all play it. “The government will not protect the economic interests of the German people by the circuitous method of an economic bureaucracy to be organised by the state, but by the utmost furtherance of private initiative and by the recognition of the rights of property,” Hitler told the Reichstag in 1933. Not exactly the words of a man about to break into a rendition of “The Red Flag”.

But does it matter? Yes, it does, actually. Hitler wasn’t a socialist, nor was he a conservative. He was a political mutation. And to try to place him anywhere on the conventional political spectrum is not just to abuse history but to play a dangerous game with the future.

Hitler has gone but his progeny are very much alive. In Hungary, they are calling for a register of Jews to be drawn up. One, a mass murderer, is languishing in a Norwegian jail. A few are pushing their leaflets through the front doors on east London housing estates.

There is one thing political extremists crave more than anything else and that is entry to the mainstream – and by branding such people “socialists” or “conservatives” we unlatch the door and pull back the bolt.

Hitler was Hitler, a grotesque one-off. Or he will be, if we avoid bestowing unnecessary respectability on those who dream of following him.